A number of companies have rushed to release a patch after The Register revealed the severe design flaw in Intel microprocessors that allows sensitive data, such as passwords and crypto-keys, to be stolen from memory.

As well as Microsoft deployment of fixes to Azure, Amazon has updated its AWS Linux guest kernels to protect customers against Meltdown, while Google recommends its cloud users apply necessary patches and reboot their virtual machines.

A Microsoft spokeswoman said: "We’re aware that some customers are experiencing difficulty with their virtual machines as we complete the security update. These are isolated incidents and we are working directly with customers to address each one.” ®